1. Technical Field
The invention relates to attachment devices and in particular to a self locking, snap mounted attachment device intended primarily for use for mounting the end members of an air spring between two spaced support members without additional attachment fasteners.
2. Background Information
Air springs consisting of a pair of spaced end members and an intervening flexible sleeve or bellows which forms an internal pressurized fluid chamber, have been used for many applications, such as mounting between spaced components of a vehicle for absorbing road shock, supporting parts of machines and equipment such as presses on which shock forces are continually imparted, and for regulating and maintaining the spacing between two spaced components of various pieces of equipment. These air springs assume various configurations depending upon their particular application. Such air springs usually consist of one end member which is an end cap with the other end member being a piston. The piston usually has a conical outer surface over which a rolling lobe of the flexible bellows moves for affecting the damper of the vehicle or equipment on which the air spring is mounted. Some examples of such prior art air springs are shown in U.S. Pat. Nos. 4,564,177, 4,787,606 and 4,852,861.
Heretofore, these air springs were attached to the spaced supporting members, and in particular to the spaced components of a vehicle, by various attachment bolts or fasteners which extend into the piston and end cap such as shown in certain of the above referenced patents.
However, for certain applications, due to the limited space available for mounting the air springs within a vehicle and the inaccessibility of the air spring mounting supports or brackets, difficulties are encountered in reaching both ends of the air spring for securing the same to the supporting structures by usual attachment bolts. Also, the use of separate attachment bolts, even if access is possible, requires additional equipment and manpower for securing the bolts to the air springs.
Therefore, the need exists for an improved attachment device for mounting a first member such as an end cap of an air spring onto a supporting structure, and in particular for mounting the end cap and piston of an air spring onto spaced supports within a vehicle without separate attachment bolts or fasteners.
Various types of self locking or snap mounted attachment devices have been developed in the past for various applications, examples of which are shown in the following patents.
U.S. Pat. No. 3,169,292 discloses a snap fastener which includes a stud element having beveled surfaces which joins a neck and a large diameter surface. The beveled surface will facilitate removal of the stud from the socket opening. A bulbous head has a curved cam surface which facilitates attachment of the fastener to the socket.
U.S. Pat. No. 3,415,155 discloses a bushing formed of plastic having resilient ears which project radially outwardly from a main body of the bushing adjacent one end, and has a radial annular shoulder on the bushing adjacent the other end which is snap fitted through a hole in a plate when inserted through the hole with the ears remaining on the exterior of the plate, afterwhich a pin is snap fitted into the bushing.
U.S. Pat. No. 3,476,008 discloses a fastener having a shoulder portion that facilitates secure attachment of the fastener. The stud fastener has a disc shaped head and legs which have shoulders which extend through a support aperture to engage edges of the aperture and attach the fastener to the support.
U.S. Pat. No. 3,818,729 discloses a brake yoke rod retainer for an automatic washer which has a plurality of segments which have frustoconical surfaces which are formed as angled cam surfaces to facilitate installation and removal of the retainer on the washer.
U.S. Pat. No. 4,012,155 discloses a snap lock connector in which a male member of the connector has leading and camming surfaces which correspond to leading and camming surfaces of a female member. These camming surfaces facilitate the insertion and withdrawal of the male member within the female member. The connector is used principally for assembling furniture to facilitate storage and shipping.
U.S. Pat. No. 4,804,303 discloses an attachment block assembly that is connected to a support structure by use of resilient leg elements. A base component is forcibly removed from the frame plate by flexing the resilient legs inwardly so that a latch member will be allowed to glide over the edge of an opening. The snap fastener legs each have a cam surface to facilitate removal and insertion of the fastener from a plate.
U.S. Pat. No. 4,739,543 discloses a push pin fastener for securing automotive trim to an automobile body. The fastener includes two cantilevered arms or legs having locking surfaces which facilitate insertion of the pin and prevent removal once inserted.
U.S. Pat. No. 5,005,265 discloses a two piece stud assembly in which the stud has a plurality of angled flexible camming members engaged within a counterboard receiving aperture of a second member for securing the stud within the bushing for attaching two members together.
Although many of the prior art self locking, snap mounted attachment devices perform satisfactory for their intended purpose, they would not be suitable for applications in which the attached device would experience shear forces, which forces are exerted in a generally radial direction on the attachment device, in addition to resisting longitudinal or axial pull out of the device from the attachment members. Most of the known prior art fasteners and attachment devices provide an easy means of attaching a member to a supporting structure by the use of flexible, cam actuated members. However these flexible members are not able to resist shear loading due to the flexible fingers or tabs being unable to resist such forces without becoming loose or breaking in the supporting structure.
Therefore, the need exists for an improved attachment device which permits the ease of assembly of a member onto an attachment member, and in particular for securing an air spring between two spaced supports, in which the attachment device is able to withstand radial shear forces without loosening of the mounted member or lessening of the retention of the securement fingers with respect to the mounting structures.